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Declaration emit for inlined mapped types preserves modifier-preserving behavior (#55054)
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‎src/compiler/checker.ts

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@@ -6641,6 +6641,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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const questionToken = type.declaration.questionToken ? factory.createToken(type.declaration.questionToken.kind) as QuestionToken | PlusToken | MinusToken : undefined;
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let appropriateConstraintTypeNode: TypeNode;
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let newTypeVariable: TypeReferenceNode | undefined;
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// If the mapped type isn't `keyof` constraint-declared, _but_ still has modifiers preserved, and its naive instantiation won't preserve modifiers because its constraint isn't `keyof` constrained, we have work to do
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const needsModifierPreservingWrapper = !isMappedTypeWithKeyofConstraintDeclaration(type)
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&& !(getModifiersTypeFromMappedType(type).flags & TypeFlags.Unknown)
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&& context.flags & NodeBuilderFlags.GenerateNamesForShadowedTypeParams
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&& !(getConstraintTypeFromMappedType(type).flags & TypeFlags.TypeParameter && getConstraintOfTypeParameter(getConstraintTypeFromMappedType(type))?.flags! & TypeFlags.Index);
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if (isMappedTypeWithKeyofConstraintDeclaration(type)) {
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// We have a { [P in keyof T]: X }
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// We do this to ensure we retain the toplevel keyof-ness of the type which may be lost due to keyof distribution during `getConstraintTypeFromMappedType`
@@ -6651,6 +6656,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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}
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appropriateConstraintTypeNode = factory.createTypeOperatorNode(SyntaxKind.KeyOfKeyword, newTypeVariable || typeToTypeNodeHelper(getModifiersTypeFromMappedType(type), context));
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}
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else if (needsModifierPreservingWrapper) {
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// So, step 1: new type variable
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const newParam = createTypeParameter(createSymbol(SymbolFlags.TypeParameter, "T" as __String));
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const name = typeParameterToName(newParam, context);
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newTypeVariable = factory.createTypeReferenceNode(name);
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// step 2: make that new type variable itself the constraint node, making the mapped type `{[K in T_1]: Template}`
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appropriateConstraintTypeNode = newTypeVariable;
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}
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else {
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appropriateConstraintTypeNode = typeToTypeNodeHelper(getConstraintTypeFromMappedType(type), context);
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}
@@ -6672,6 +6685,18 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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factory.createKeywordTypeNode(SyntaxKind.NeverKeyword)
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);
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}
6688+
else if (needsModifierPreservingWrapper) {
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// and step 3: once the mapped type is reconstructed, create a `ConstraintType extends infer T_1 extends keyof ModifiersType ? {[K in T_1]: Template} : never`
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// subtly different from the `keyof` constraint case, by including the `keyof` constraint on the `infer` type parameter, it doesn't rely on the constraint type being itself
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// constrained to a `keyof` type to preserve its modifier-preserving behavior. This is all basically because we preserve modifiers for a wider set of mapped types than
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// just homomorphic ones.
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return factory.createConditionalTypeNode(
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typeToTypeNodeHelper(getConstraintTypeFromMappedType(type), context),
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factory.createInferTypeNode(factory.createTypeParameterDeclaration(/*modifiers*/ undefined, factory.cloneNode(newTypeVariable!.typeName) as Identifier, factory.createTypeOperatorNode(SyntaxKind.KeyOfKeyword, typeToTypeNodeHelper(getModifiersTypeFromMappedType(type), context)))),
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result,
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factory.createKeywordTypeNode(SyntaxKind.NeverKeyword)
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);
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}
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return result;
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}
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‎tests/baselines/reference/inlineMappedTypeModifierDeclarationEmit.js

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//// [tests/cases/compiler/inlineMappedTypeModifierDeclarationEmit.ts] ////
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//// [index.ts]
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import { test1, test2 } from "./other";
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export function wrappedTest1<T, K extends string>(obj: T, k: K) {
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return test1(obj, k);
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}
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export function wrappedTest2<T, K extends string>(obj: T, k: K) {
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return test2(obj, k);
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}
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export type Obj = {
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a: number;
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readonly foo: string;
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};
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export const processedInternally1 = wrappedTest1({} as Obj, "a");
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export const processedInternally2 = wrappedTest2({} as Obj, "a");
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//// [other.ts]
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// how Omit from lib is defined
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type OmitReal<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
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// what we see when we hover it
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type OmitUnveiled<T, K extends string | number | symbol> = {
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[P in Exclude<keyof T, K>]: T[P];
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};
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export function test1<T, K extends string>(obj: T, k: K): OmitReal<T, K> {
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return {} as any;
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}
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export function test2<T, K extends string>(obj: T, k: K): OmitUnveiled<T, K> {
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return {} as any;
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}
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//// [other.js]
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"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.test2 = exports.test1 = void 0;
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function test1(obj, k) {
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return {};
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}
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exports.test1 = test1;
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function test2(obj, k) {
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return {};
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}
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exports.test2 = test2;
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//// [index.js]
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"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.processedInternally2 = exports.processedInternally1 = exports.wrappedTest2 = exports.wrappedTest1 = void 0;
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var other_1 = require("./other");
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function wrappedTest1(obj, k) {
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return (0, other_1.test1)(obj, k);
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}
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exports.wrappedTest1 = wrappedTest1;
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function wrappedTest2(obj, k) {
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return (0, other_1.test2)(obj, k);
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}
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exports.wrappedTest2 = wrappedTest2;
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exports.processedInternally1 = wrappedTest1({}, "a");
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exports.processedInternally2 = wrappedTest2({}, "a");
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//// [other.d.ts]
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type OmitReal<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
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type OmitUnveiled<T, K extends string | number | symbol> = {
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[P in Exclude<keyof T, K>]: T[P];
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};
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export declare function test1<T, K extends string>(obj: T, k: K): OmitReal<T, K>;
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export declare function test2<T, K extends string>(obj: T, k: K): OmitUnveiled<T, K>;
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export {};
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//// [index.d.ts]
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export declare function wrappedTest1<T, K extends string>(obj: T, k: K): Exclude<keyof T, K> extends infer T_1 extends keyof T ? { [P in T_1]: T[P]; } : never;
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export declare function wrappedTest2<T, K extends string>(obj: T, k: K): { [P in Exclude<keyof T, K>]: T[P]; };
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export type Obj = {
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a: number;
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readonly foo: string;
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};
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export declare const processedInternally1: {
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readonly foo: string;
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};
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export declare const processedInternally2: {
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foo: string;
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};

‎tests/baselines/reference/inlineMappedTypeModifierDeclarationEmit.symbols

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//// [tests/cases/compiler/inlineMappedTypeModifierDeclarationEmit.ts] ////
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=== index.ts ===
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import { test1, test2 } from "./other";
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>test1 : Symbol(test1, Decl(index.ts, 0, 8))
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>test2 : Symbol(test2, Decl(index.ts, 0, 15))
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export function wrappedTest1<T, K extends string>(obj: T, k: K) {
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>wrappedTest1 : Symbol(wrappedTest1, Decl(index.ts, 0, 39))
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>T : Symbol(T, Decl(index.ts, 2, 29))
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>K : Symbol(K, Decl(index.ts, 2, 31))
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>obj : Symbol(obj, Decl(index.ts, 2, 50))
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>T : Symbol(T, Decl(index.ts, 2, 29))
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>k : Symbol(k, Decl(index.ts, 2, 57))
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>K : Symbol(K, Decl(index.ts, 2, 31))
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return test1(obj, k);
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>test1 : Symbol(test1, Decl(index.ts, 0, 8))
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>obj : Symbol(obj, Decl(index.ts, 2, 50))
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>k : Symbol(k, Decl(index.ts, 2, 57))
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}
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export function wrappedTest2<T, K extends string>(obj: T, k: K) {
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>wrappedTest2 : Symbol(wrappedTest2, Decl(index.ts, 4, 1))
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>T : Symbol(T, Decl(index.ts, 6, 29))
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>K : Symbol(K, Decl(index.ts, 6, 31))
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>obj : Symbol(obj, Decl(index.ts, 6, 50))
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>T : Symbol(T, Decl(index.ts, 6, 29))
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>k : Symbol(k, Decl(index.ts, 6, 57))
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>K : Symbol(K, Decl(index.ts, 6, 31))
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return test2(obj, k);
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>test2 : Symbol(test2, Decl(index.ts, 0, 15))
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>obj : Symbol(obj, Decl(index.ts, 6, 50))
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>k : Symbol(k, Decl(index.ts, 6, 57))
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}
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export type Obj = {
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>Obj : Symbol(Obj, Decl(index.ts, 8, 1))
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a: number;
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>a : Symbol(a, Decl(index.ts, 10, 19))
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readonly foo: string;
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>foo : Symbol(foo, Decl(index.ts, 11, 12))
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};
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export const processedInternally1 = wrappedTest1({} as Obj, "a");
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>processedInternally1 : Symbol(processedInternally1, Decl(index.ts, 15, 12))
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>wrappedTest1 : Symbol(wrappedTest1, Decl(index.ts, 0, 39))
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>Obj : Symbol(Obj, Decl(index.ts, 8, 1))
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export const processedInternally2 = wrappedTest2({} as Obj, "a");
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>processedInternally2 : Symbol(processedInternally2, Decl(index.ts, 16, 12))
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>wrappedTest2 : Symbol(wrappedTest2, Decl(index.ts, 4, 1))
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>Obj : Symbol(Obj, Decl(index.ts, 8, 1))
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=== other.ts ===
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// how Omit from lib is defined
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type OmitReal<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
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>OmitReal : Symbol(OmitReal, Decl(other.ts, 0, 0))
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>T : Symbol(T, Decl(other.ts, 1, 14))
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>K : Symbol(K, Decl(other.ts, 1, 16))
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>Pick : Symbol(Pick, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(other.ts, 1, 14))
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>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(other.ts, 1, 14))
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>K : Symbol(K, Decl(other.ts, 1, 16))
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// what we see when we hover it
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type OmitUnveiled<T, K extends string | number | symbol> = {
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>OmitUnveiled : Symbol(OmitUnveiled, Decl(other.ts, 1, 69))
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>T : Symbol(T, Decl(other.ts, 3, 18))
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>K : Symbol(K, Decl(other.ts, 3, 20))
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[P in Exclude<keyof T, K>]: T[P];
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>P : Symbol(P, Decl(other.ts, 4, 3))
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>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(other.ts, 3, 18))
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>K : Symbol(K, Decl(other.ts, 3, 20))
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>T : Symbol(T, Decl(other.ts, 3, 18))
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>P : Symbol(P, Decl(other.ts, 4, 3))
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};
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export function test1<T, K extends string>(obj: T, k: K): OmitReal<T, K> {
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>test1 : Symbol(test1, Decl(other.ts, 5, 2))
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>T : Symbol(T, Decl(other.ts, 7, 22))
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>K : Symbol(K, Decl(other.ts, 7, 24))
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>obj : Symbol(obj, Decl(other.ts, 7, 43))
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>T : Symbol(T, Decl(other.ts, 7, 22))
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>k : Symbol(k, Decl(other.ts, 7, 50))
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>K : Symbol(K, Decl(other.ts, 7, 24))
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>OmitReal : Symbol(OmitReal, Decl(other.ts, 0, 0))
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>T : Symbol(T, Decl(other.ts, 7, 22))
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>K : Symbol(K, Decl(other.ts, 7, 24))
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return {} as any;
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}
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export function test2<T, K extends string>(obj: T, k: K): OmitUnveiled<T, K> {
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>test2 : Symbol(test2, Decl(other.ts, 9, 1))
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>T : Symbol(T, Decl(other.ts, 11, 22))
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>K : Symbol(K, Decl(other.ts, 11, 24))
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>obj : Symbol(obj, Decl(other.ts, 11, 43))
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>T : Symbol(T, Decl(other.ts, 11, 22))
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>k : Symbol(k, Decl(other.ts, 11, 50))
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>K : Symbol(K, Decl(other.ts, 11, 24))
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>OmitUnveiled : Symbol(OmitUnveiled, Decl(other.ts, 1, 69))
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>T : Symbol(T, Decl(other.ts, 11, 22))
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>K : Symbol(K, Decl(other.ts, 11, 24))
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return {} as any;
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}

‎tests/baselines/reference/inlineMappedTypeModifierDeclarationEmit.types

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//// [tests/cases/compiler/inlineMappedTypeModifierDeclarationEmit.ts] ////
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=== index.ts ===
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import { test1, test2 } from "./other";
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>test1 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>test2 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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export function wrappedTest1<T, K extends string>(obj: T, k: K) {
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>wrappedTest1 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>obj : T
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>k : K
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return test1(obj, k);
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>test1(obj, k) : { [P in Exclude<keyof T, K>]: T[P]; }
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>test1 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>obj : T
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>k : K
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}
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export function wrappedTest2<T, K extends string>(obj: T, k: K) {
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>wrappedTest2 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>obj : T
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>k : K
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return test2(obj, k);
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>test2(obj, k) : { [P in Exclude<keyof T, K>]: T[P]; }
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>test2 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>obj : T
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>k : K
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}
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export type Obj = {
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>Obj : { a: number; readonly foo: string; }
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a: number;
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>a : number
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readonly foo: string;
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>foo : string
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};
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export const processedInternally1 = wrappedTest1({} as Obj, "a");
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>processedInternally1 : { readonly foo: string; }
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>wrappedTest1({} as Obj, "a") : { readonly foo: string; }
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>wrappedTest1 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>{} as Obj : Obj
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>{} : {}
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>"a" : "a"
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export const processedInternally2 = wrappedTest2({} as Obj, "a");
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>processedInternally2 : { foo: string; }
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>wrappedTest2({} as Obj, "a") : { foo: string; }
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>wrappedTest2 : <T, K extends string>(obj: T, k: K) => { [P in Exclude<keyof T, K>]: T[P]; }
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>{} as Obj : Obj
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>{} : {}
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>"a" : "a"
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=== other.ts ===
60+
// how Omit from lib is defined
61+
type OmitReal<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
62+
>OmitReal : OmitReal<T, K>
63+
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// what we see when we hover it
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type OmitUnveiled<T, K extends string | number | symbol> = {
66+
>OmitUnveiled : OmitUnveiled<T, K>
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[P in Exclude<keyof T, K>]: T[P];
69+
};
70+
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export function test1<T, K extends string>(obj: T, k: K): OmitReal<T, K> {
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>test1 : <T, K extends string>(obj: T, k: K) => OmitReal<T, K>
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>obj : T
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>k : K
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return {} as any;
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>{} as any : any
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>{} : {}
79+
}
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export function test2<T, K extends string>(obj: T, k: K): OmitUnveiled<T, K> {
82+
>test2 : <T, K extends string>(obj: T, k: K) => OmitUnveiled<T, K>
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>obj : T
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>k : K
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return {} as any;
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>{} as any : any
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>{} : {}
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}

‎tests/cases/compiler/inlineMappedTypeModifierDeclarationEmit.ts

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// @declaration: true
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// @filename: index.ts
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import { test1, test2 } from "./other";
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export function wrappedTest1<T, K extends string>(obj: T, k: K) {
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return test1(obj, k);
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}
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export function wrappedTest2<T, K extends string>(obj: T, k: K) {
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return test2(obj, k);
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}
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export type Obj = {
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a: number;
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readonly foo: string;
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};
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export const processedInternally1 = wrappedTest1({} as Obj, "a");
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export const processedInternally2 = wrappedTest2({} as Obj, "a");
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// @filename: other.ts
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// how Omit from lib is defined
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type OmitReal<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
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// what we see when we hover it
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type OmitUnveiled<T, K extends string | number | symbol> = {
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[P in Exclude<keyof T, K>]: T[P];
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};
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export function test1<T, K extends string>(obj: T, k: K): OmitReal<T, K> {
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return {} as any;
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}
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export function test2<T, K extends string>(obj: T, k: K): OmitUnveiled<T, K> {
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return {} as any;
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}

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